[SI-LIST] Re: Can we use IBIS model generate SSN current?
- From: <lyndell.asbenson@xxxxxxxxxxx>
- To: <arpad.muranyi@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 3 Apr 2024 13:54:26 -0700
Has anyone done automated IBIS model on big iron ATE? -Lyndell
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf Of
arpad.muranyi @ siemens . com ("arpad.muranyi")
Sent: Wednesday, April 3, 2024 9:46 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Can we use IBIS model generate SSN current?
Robbie,
the best method is...
That all depends on how the model maker creates his/her model. SPICE models
are not necessarily better because they are SPICE models...
But yes, the modeling language may have a say in what you can or cannot model
with the language. The various modeling languages were invented to address
specific needs, usually with a tradeoff between speed and accuracy.
In some cases, "better" means more accuracy, but in other cases it might mean
orders of magnitudes faster.
To answer your question, IBIS models can be written with "power aware" features
which account for the currents going through the power and ground pins of the
device. However, if you do this with the [Model] keyword, you can only account
for the currents for the output stage of the buffer. Pre-driver or core
currents are not included in such buffer models. On the other hand, if you use
the more advanced capabilities in IBIS, the [External Model] or [External
Circuit] keywords with the associated advanced modeling languages, Verilog-A or
VHDL-AMS, you can make your model perform miracles if you like... 😊
IBIS-AMI models are somewhat different. They are basically based on signal
processing algorithms, using an impulse response of the channel. This impulse
response is a snapshot of the channel, like a single frame from a long video.
The signal processing algorithms in the AMI model takes this "still picture"
and tries to make a movie out of it, however, this movie may not end up with
the same details that were in the original video...
IBIS-AMI models rely on the assumption that the channel is LTI (linear and time
invariant). Time invariance means that the power supply voltages do not change
during the time of the "simulation". If you want to simulate the effects of
power fluctuations, you need to ask your model vendor to make models for you
which are made for that purpose. IBIS-AMI models are not necessarily the best
choice for that purpose.
I hope this gave you some insight into power aware simulations and modeling...
Thanks,
Arpad
=================================================================================================
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf Of
Luping Liu
Sent: Wednesday, April 3, 2024 5:22 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Can we use IBIS model generate SSN current?
Hi Experts：
When we do DDR SI+PI co-simulation， the best method is use spice model to
generate the VDDQ current .
But most of time , we only have IBIS/AMI model on hand , my question is ,
is IBIS can be, or will be used to mimic the current draw from the VDDQ PDN?
I see many application are focus on the PDN noise impact to IO jitter with
IBIS model , but rarely see the reverse operation , does any reasearch on this
area?
Thanks and Regards,
Robbie
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